Optical scanners are well-known in the art and produce machine-readable data which is representative of the image of an object, e.g. a page of printed text. Optical scanners generally employ line-focus systems which image an object by sequentially focusing narrow "scan line" portions of the object onto a linear photosensor array by sweeping a scanning head over the object.
In a line-focus system, a light beam from an illuminated line object is imaged by a lens on a linear photosensor array which is positioned remotely from the line object. The linear photosensor array is a single dimension array of photoelements which correspond to small area locations on the line object. These small area locations on the line object are commonly referred to as "picture elements" or "pixels." In response to light from its corresponding pixel location on the line object, each photosensor pixel element in the linear photosensor array (sometimes referred to simply as "pixels") produces a data signal which is representative of the light intensity that it experiences during an immediately preceding interval of time known as a sampling interval. All of the photoelement data signals are received and processed by an appropriate data processing system.
In a color optical scanner, a plurality of spectrally separated imaging beams (typically red, green and blue beams) must be projected onto photosensor arrays. Some color optical scanners employ beam splitter devices for spectrally separating an imaging light beam into color component beams. These separate color component beams are projected onto separate linear photosensor arrays. Other optical scanners project color component images on a single linear array in a series of separate scanning passes.
The construction and operation of color optical scanners employing beam splitter assemblies and photosensor arrays are fully disclosed in the following United States patents: U.S. Pat. Nos. 4,870,268 of Vincent et al. for COLOR COMBINER AND SEPARATOR AND IMPLEMENTATIONS; 4,926,041 of Boyd for OPTICAL SCANNER (and corresponding EPO patent application no. 90306876.5 filed Jun. 22, 1990); 5,019,703 of Boyd et al. for OPTICAL SCANNER WITH MIRROR MOUNTED OCCLUDING APERTURE OR FILTER (and corresponding EPO patent application no. 90312893.2 filed Nov. 27, 1990); 5,032,004 of Steinle for BEAM SPLITTER APPARATUS WITH ADJUSTABLE IMAGE FOCUS AND REGISTRATION (and corresponding EPO patent application no. 91304185.1 filed May 9, 1991); 5,044,727 of Steinle for BEAM SPLITTER/COMBINER APPARATUS (and corresponding EPO patent application no. 91303860.3 filed Apr. 29, 1991); 5,040,872 of Steinle for BEAM SPLITTER/COMBINER WITH PATH LENGTH COMPENSATOR (and corresponding EPO patent application no. 90124279.2 filed Dec. 14, 1990 which has been abandoned); and 5,227,620 of Elder, Jr. et al. for APPARATUS FOR ASSEMBLING COMPONENTS OF COLOR OPTICAL SCANNERS (and corresponding EPO patent application no. 91304403.8 filed May 16, 1991), 5,410,347 of Steinle et al. for COLOR OPTICAL SCANNER WITH IMAGE REGISTRATION HOLDING ASSEMBLY which are all hereby specifically incorporated by reference for all that is disclosed therein.
A hand-held optical scanning device is an optical scanner which is moved across a scanned object, e.g. a page of text, by hand. Rollers may be provided on a hand-held scanning device to guide the device across the object to be scanned and also to provide data to the scanning device microprocessor regarding the speed at which the scanning device is being moved over the scanned object. These rollers may also serve to control the speed at which an operator moves the scanning device across the scanned object.
The construction and operation of hand-held optical scanning devices employing such rollers is fully disclosed in U.S. Pat. Nos. 5,306,908 of McConica et al. for MANUALLY OPERATED HAND-HELD OPTICAL SCANNER WITH TACTILE SPEED CONTROL ASSEMBLY (and corresponding EPO patent application no. 94301507.3 filed Mar. 2, 1994); and 5,381,020 of Kochis et al. for HAND-HELD OPTICAL SCANNER WITH ONBOARD BATTERY RECHARGING ASSEMBLY, which are all hereby specifically incorporated by reference for all that is disclosed therein.
Optical systems for hand-held scanning devices must generally be very compact due to the relatively small size of hand-held scanning devices. The construction and operation of such an optical system for a hand-held optical scanning device is fully disclosed in U.S. Pat. No. 5,552,597 of McConica for LIGHT PATH FOR HAND-HELD SCANNER, which is hereby specifically incorporated by reference for all that is disclosed therein.
The size of a hand-held scanning device generally corresponds to the size of the objects to be scanned. For example, if 8.5 inch by 11 inch documents are to be scanned, then the length of the scanning device must generally be greater than 8.5 inches. It has been found, however, that a scanning device of this size is unwieldy to transport. A hand-held scanning device having such a minimum dimension could not, for example, conveniently be carried in a user's pocket.
To avoid this problem and achieve a greater degree of compactness, some hand-held scanning devices are constructed smaller than the size of the objects to be scanned. In order to scan the entire object, the user is required to "sweep" such a scanning device over all parts of the object. Circuitry within the scanning device then assembles or "stitches" the image portions together in order to obtain a complete image of the scanned object.
Although relatively compact, this type of hand-held scanning device has its drawbacks. The stitching function required in this type of device, for example, is relatively complex and generally results in severely reduced image quality. Also, the required multiple pass sweeping operation is relatively slow compared to that provided by a full-width single pass scanning device. In addition, many users find the multiple pass scanning to be generally inconvenient.